Tractors and Related Equipment

TRACTOR USES 

Tractors have manyheir uses as construct construction ion equipment. While their primary purpose m ay be to pull or push loads, they are also used as mounts for many types of accessories, such as front-end shovels, rippers, bulldozer blades, side booms, hoes, trenches, etc.

Types of Tractors 

Tractors maybe divided into two major types: 1. Crawler 2. Wheel - wheel tractor are either two-wheel or four-wheel.

Factors to be Considered in selecting Tractor 1. The size required for a job 2. The kind of job for which it will be used. 3. The type of footing over which it will operate. 4. The firmness of the haul road 5. The smoothness of the haul road 6. The slope of the haul road 7. The length of the haul 8. The type of work it will do after this job is

completed

CRAWLER TRACTORS

Crawler tractors are usually rated by size or weight and power. The weight is important on many projects because the maximum tractive force that a unit can provide is limited to the productof the weight times the coefficient of traction for the unit.

Crawler Tractors with direct drive Some manufacturers specifications list two sets of drawbar pullsrated and maximum. The rated is the drawbar pull that can be sustained for continuous operation, while the maximum is the drawbar pull that the tractor can exert for a short period while lugging the engine.

WHEEL TRACTORS

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In civil engineering, a wheel tractor-scraper is a piece of  heavy equipment used for earthmoving. A scraper is a large piece of equipment used in the mines.The rear part has a vertically moveable hopper (also known as the bowl) with a sharp horizontal front edge. The hopper can be hydraulically lowered and raised. When the hopper is lowered, the front edge cuts into the soil or clay like a plane and fills the hopper. When the hopper is full (8 to 34 m3 or 10 to 44 cu yd heaped, depending on type) it is raised, and closed with a vertical blade (known as the apron). The scraper can transport its load to the fill area where the blade is raised, the back panel of the hopper, or the ejector, is hydraulically pushed forward and the load tumbles out. Then the empty scraper returns to the cut site and repeats the cycle.

Gradability 

It is defined as the maximum slope, expressed as a percent, up which a crawler or wheel-type prime mover may move at a uniform speed. The gradability may be determined for an empty or loaded vehicle.

The forward motion of a prime mover is limited by the following factors 1.

The power developed by the engine and available as drawbar pull or rimpull

2.

The rolling resistance of the haul roasd

3.

The gross weight of the prime mover and its load

4.

The grade to be negotiated. Adverse grade adds to the resistance, while favorable grade subtracts from the resistance.

BULLDOZERS

General information 

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A bulldozer is a crawler (continuous tracked tractor) equipped with a substantial metal plate (known as a blade) used to push large quantities of soil, sand, rubble, or other such material during construction or conversion work and typically equipped at the rear with a claw-like device (known as a ripper) to loosen densely-compacted materials. Bulldozers can be found on a wide range of sites, mines and quarries, military bases, heavy industry factories, engineering projects and farms. The term "bulldozer" is often used erroneously to mean any heavy equipment (sometimes a loader and sometimes an excavator), but precisely, the term refers only to a tractor (usually tracked) fitted with a dozer blade.

Operation that Bulldozers are involve. 1. Clearing the land of timber and stumps 2. Opening up pilot roads through mountains and 3. 4. 5. 6. 7. 8. 9.

rocky terrain Moving earth for a haul distances up to approximately 300ft Helping load tractor-pulled scraper Spreading earthfill Backfilling trenches Clearing construction sites of debris Maintaining haul roads Clearing the floors to borrow and quarry pits

hydraulic-controlled bulldozers

Crawler-mounted versus wheelmounted Bulldozers

Crawler-mounted bulldozers advantage 1. Ability to deliver greater tractive effort 2. Ability to travel on muddy surfaces 3. Ability to travel over rough surfaces 4. Ability to operate in rocky formations 5. Greater flotation because the lower

pressures under the tracks 6. Greater use versatility on jobs

Wheel-mounted bulldozers advantages 1. Higher travel speeds on the job or from one job 2.

3. 4. 5.

to another Elimination of hauling equipment to transport the bulldozer to a job Greater output, specially when considerable traveling is necessary Less operator fatigue Ability to travel on paved highways without damaging the surface

Crawler-tractor-mounted Bulldozer

Wheel-tractor-mounted Bulldozer

Computing the output of bulldozers

CLEARING LAND

Land clearing operations 1. Complete removal of all trees and stumps, 2. 3. 4. 5.

including roots Removing all vegetation above the surface of  the ground only Disposing of vegetation by stocking and burning it Knocking all vegetation down the chopping or crushing it to or into the surface of the ground Killing or retarding the growth of brush by cutting the roots below the surface of the ground

Types of equipment used 1. Tractor-mounted bulldozers 2. Tractor-mounted special blades 3. Tractor-mounted rakes 4. Tractor-pulled chains and steel cables 5. Special machines with pusher bars, and

drum-type wheels equipped with blades to chop the vegetation as the machine passes over it.

Land-clearing blade

Tractor-mounted V blade

Tractor-mounted V blade spitting large tree

Tractor-mounted landclearing rake

Tractor-mounted clamp rake

Tractor-pulled chain

Tractor-pulled root plow

Tree-shredding machine

Tractor-mounted grapple shear

Tractor-mounted clearing blade

Ripping rock The major developments that are responsible for the increase in ripping rock 1. More powerful tractors 2. Improvements in the sizes and performances of 

rippers 3. Better instruments for determining the rip ability of rocks 4. Improved techniques in using instruments and equipment

Ripper The ripper is the long clawlike device on the back of  the bulldozer. Rippers can come as a single (single shank/giant ripper) or in groups of  two or more (multi shank rippers). Usually, a single shank is preferred for heavy ripping. The ripper shank is fitted with a replaceable tungsten ste el alloy tip.

Front-end-loaders This are used extensively in construction work to handle and transport bulk material, such as earth and rock, to load trucks, to excavate earth, as bulldozers.

Front-end loader

Articulated wheel-tractor-mounted loader